Regulations related to renewable fuels provide an example of how product requirements can change over time. The United States, Canada, and the European Union have recently increased and/or are likely to increase the required amount of product from renewable sources that is contained in transportation fuels. Based on such regulatory requirements, fuels from vegetable, animal, or algae sources such as “biodiesel” will become increasingly important as a refinery product. As a result, methods are needed that will allow existing refinery equipment to produce suitable transportation fuels that incorporate increasing amounts of renewable components.
Unfortunately, the differences in chemical composition between renewable carbon sources and mineral sources pose some difficulties for refinery processing. For example, typical biologically-derived sources for fuels have oxygen contents of 1 wt % or more, possibly as much as 10 wt % or more. Conventional hydroprocessing methods can remove oxygen from a feedstock, but the by-products from deoxygenation can lead to catalyst poisoning and/or contaminant build-up in a reaction system.
One potential feedstock source for making renewable diesel products is to use a feedstock that contains triglycerides. Triglycerides are present in many typical sources used as feedstock for making renewable products. Typical triglycerides useful for making renewable products include a three carbon glycerol backbone that has ester linkages to three longer side chains. Separating the side chains from the glycerol backbone typically results in formation of a fatty acid corresponding to each of the side chains. After separation from the glycerol backbone, the fatty acids can have a chain length that is suitable for use, possibly after further processing, in diesel products such as diesel fuels or diesel fuel additives.
U.S. Patent Application Publication 2010/0163458 describes a method for converting effluents of renewable origin into fuel. The method includes the use of a supported catalyst containing MoS2 and a dopant, such as phosphorus, carbon, or silicon. The method is described as favoring removal of oxygen by hydrodeoxygenation as opposed decarbonylation or decarboxylation.
U.S. Patent Application Publication 2011/0166396 describes a hydrodeoxygenation catalyst and a method for using such a catalyst. The catalyst is a supported catalyst containing Mo, with a support that includes a bimodal pore distribution. Additionally, at least 2 volume percent of the pores in the support are greater than 50 nm in diameter. The Mo catalyst with the specified pore distribution is used to perform hydrodeoxygenation on feeds containing up to 35 vol. % of renewable organic material.
U.S. Patent Application Publication 2010/0270207 describes a two stage method for processing or co-processing biomass oil containing triglycerides. The first stage includes a catalyst including only a Group VIB metal for performing hydroconversion of the triglycerides. A second stage includes a conventional hydrotreating catalyst including a Group VIB and a Group VIII metal for performing other hydroconversion reactions, such as olefin saturation and heteroatom removal.